The dramatic increase in the prevalence of antibiotic resistance among important hospital- and community-acquired bacterial pathogens poses a serious threat to our ability to effectively treat infectious diseases. This growing problem necessitates the development of novel antibacterial agents that are not subject to existing mechanisms of resistance. However, recent efforts to identify novel antibacterial targets and screen for target-specific inhibitors in large synthetic compound libraries have been largely unsuccessful. Because the majority of existing antibiotics are derived from natural sources, there is a renewed interest in screening unique sources of natural products for novel antibacterial compounds. To address the need for novel antibiotics, we will identify and purify antibacterial compounds from extracts derived from the fruiting bodies of basidiomycetes and ascomycetes (mushrooms). This represents a unique source of natural products has not been systematically screened for antibacterial compounds. LifePharms has developed an extensive collection of nearly 200,000 prefractionated natural product extracts derived from over 26,000 unique fungal species. In collaboration with Microbiotix, Inc. a small portion of the library has been screened for antibacterial activity. The preliminary screens indentified fractions from three fungal species with antibacterial activity against Staphylococcus aureus. The activities in these fractions have been partially purified, and preliminary antibacterial activity assays have demonstrated potency against a panel antibiotic-resistant Gram-positive pathogens. Our strategy is to further purify and characterize these active compounds for antibacterial activity and chemical novelty, and to continue screening the extensive LifePharms library for novel antibiotics. Our goal is to identify novel natural products derived from mushroom extracts with potent antibacterial activity, and to develop them into novel antibiotics to treat resistant organisms. In Phase I, we will purify the antibacterial compounds identified in preliminary screens, determine their structures, and evaluate them in a panel of assays designed to measure antibacterial activity, cytotoxicity, and mechanism of action. In order to provide additional compounds for these analyses, we will screen the remainder of the LifePharms collection of extracts for antibacterial compounds. Purified compounds that have a unique structure and meet the specified criteria for potency, selectivity, and mechanism of action will be developed further in Phase II PUBLIC HEALTH RELEVANCE: The dramatic increase in the prevalence of antibiotic resistance among important hospital- and community-acquired bacterial pathogens poses a serious threat to our ability to effectively treat infectious diseases. , We will identify and purify antibacterial compounds from extracts derived from the fruiting bodies of basidiomycetes and ascomycetes (mushrooms).